Doctors for paper making machines

ABSTRACT

The invention provides a doctor for a paper making machine in which the holder for the doctor blade carries a series of spaced members which are individually adjustable, without any distortion of the blade holder itself, to vary the doctoring pressure applied by the blade at different zones along its length.

United States Patent Grimston et al.

1 51 Mar. 21, 1972 [54] DOCTORS FOR PAPER MAKING MACHINES [72] Inventors: Roger Anthony Grlmston, Hemel Hempstead; Albert Henry John Boyland, London, both of England [73] Assignee: Vlckerys Llmlted, London, England [22] Filed: Sept. 26, 1969 [21] Appl. No.: 861,409

[30] Foreign Application Priority Data Oct. 1, 1968 Great Britain ..46,588/68 US. Cl ..l5/256.51

...D21g 3/00, D21 g 3/02, D21 g 3/04 Field of Search 15/2565 1, 256.5; 100/174 [56] References Cited UNITED STATES PATENTS 767,933 8/1904 Galleciez 15/256.5 1 1,803,927 5/1931 Vedder l 5/256.5l 2,477,339 7/1949 Ljungquist.. 15/256.5l 2,664,792 1/1954 Cook ..l5/256.51

FOREIGN PATENTS OR APPLlCATlONS 656,812 9/1951 Great Britain 151256.51

Primary Examiner-Leon G. Machlin Attorney-Watson, Cole, Grindle & Watson [5 7] ABSTRACT The invention provides a doctor for a paper making machine in which the holder for the doctor blade carries a series of spaced members which are individually adjustable, without any distortion of the blade holder itself, to vary the doctoring pressure applied by the blade at different zones along its length.

7 Claims, 6 Drawing Figures PATENTEDHARZI I972 3.649.991

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PATENTEDMARZI m2 SHEET 2 [IF 2 Q l I DOCTORS FOR PAPER MAKING MACHINES For the efficient doctoring of rolls and cylinders in papermaking it is essential that the doctor blade should be in even contact with the roll surface over its whole length. Furthermore, it is desirable that the contact pressure should not vary unduly along the roll face.

Some rolls are cambered, that is to say the diameter increases from the ends towards the center. Other rolls, and particularly cylinders, are heated with the result that the diameter tends to increase unevenly as the cylinder expands. Again where light weight is required, and where a roll is long, the roll may deflect under its own weight since it is only supported at the ends. Furthermore, it is sometimes found that the doctor support has uneven surfaces and/or deflects in the center. All .these factors militate against a consistent doctor blade contact pressure along the whole length of the roll.

It has been proposed to provide for compensation for camber or deflection of the roll or cylinder by making provision for local distortion or warping of the blade holder which carries the doctor blade, but this expedient is not very satisfactory because the holder is of fairly massive construction and does not easily distort.

The invention provides a doctor for a papermaking machine in which the holder for the doctor blade carries a series of spaced members which are individually adjustable, without any distortion of the blade holder itself, to vary the doctoring pressure applied by the blade at different zones along its length.

Thus the blade holder may carry a series of spaced adjusting screws which are individually adjustable to effect variation of the level at different points along its length either of the rear end of the doctor blade itself or of the rear end of a pressure plate, mounted in the blade holder, which applies pressure to the doctor blade.

Certain embodiments of the invention will now be described in detail, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of part of one form of doctor according to the invention,

FIG. 2 is a cross-sectional view of the doctor shown in FIG. I, and

FIGS. 3-6 are cross-sectional views similar to that of FIG. 2 showing alternative forms of doctor.

Like reference numerals designate like parts throughout the Figures.

In the construction shown in FIGS. 1 and 2 the doctor includes a doctor blade 10, a pressure plate 11, and a blade holder made of two parts 12, 13 suitably secured together. Screws 14 are screwed at intervals, for example of 3 inches, into the upper part 12 of the blade holder and have at their lower ends heads 15, accommodated in a recess 16 in the lower part 13, which bear against the undersurface of the rear end of the pressure plate 11. The screws 14 are individually adjustable and when any screw is raised it will cause the adjacent portion of the pressure plate 11 to rock about the nose 17 of the blade holder to increase the local pressure applied by the pressure plate to the doctor blade and therefore the doctoring pressure applied to the roll 18. The screws 14 are provided with any convenient form of thread lock to ensure their retention in adjusted position, e.g., a longitudinal strip of nylon inserted into the threads which will ensure firm engagement with the corresponding threads in the blade holder.

In the construction shown in FIG. 3 the screws 14 are fitted into the lower part 13 of the blade holder and bear against the undersurface of the doctor blade 10. Upon adjustment of a screw 14 the adjacent part of the blade 10 rocks about the forward end of the pressure plate 11.

FIG. 4 shows a very similar construction, the screws 14 again being fitted into the lower part of the blade holder, but in this case the screws bear against the undersurface of the pressure plate 11.

As a further alternative and as shown in FIG. 5, instead of providing for direct engagement of the adjusting screws with the rear end of the pressure late or the doctor blade, the screws can engage a deforma le bar 20 extending longitudinally of the doctor and interposed between the screws 14 and the pressure plate 13. As a further alternative, the deformable bar may be arranged to bear against the doctor blade. Such a deformable bar provides for more even distribution of the distortion of the blade 10 resulting from adjustment of the screws 14.

FIG. 6 shows a doctor in which, as described in U.S. application No. 728,727, now U.S. Pat. No. 3,596,305, issued Aug. 3, 1971, the pressure plate 11 applies pressure to the side of the doctor blade 10 facing the roll and the screws 14 bear against the upper surface of the pressure plate.

What we claim as our invention and desire to secure by Letters Patent is:

1. Structure for doctoring a roll of a papermaking machine comprising:

an elongated, generally planar doctor blade having a Iongitudinally extending face and a longitudinal doctoring edge disposed generally in line contact with said roll;

an elongated, generally planar pressure plate having a longitudinally extending face and a longitudinal pressure edge disposed generally in line contact with the face of the blade;

a holder for the blade and the plate, said holder having an elongated abutment nose presenting a longitudinally extending fulcrum edge disposed generally in line contact with the face of the plate, said plate having a rear edge spaced from the pressure edge, said fulcrum edge contacting the plate at a location intermediate the rear edge and pressure edge thereof; and

a series of individually adjustable, longitudinally spaced members carried by the holder, said members being disposed to bear against said plate at a location adjacent its rear edge for urging the plate about said fulcrum edge to vary the pressure between said pressure edge and the blade whereby to vary the doctoring pressure applied between the doctoring edge and the roll.

2. Structure as set forth in claim 1 wherein said members comprise screws threadably engaged in said holder.

3. Structure as set forth in claim 2 wherein a deformable bar is disposed between the screws and said plate.

4. A doctor for a roll of a papennaking machine comprising a blade holder, a doctor blade accommodated in said holder for pivotal movement about its rear end with respect to the holder and adapted to bear at its front end against said roll, a pressure plate accommodated in the holder for pivotal movement about a nose on the holder which bears against the pressure plate at a location intermediate its front and rear ends, said pressure plate bearing at its front end against the doctor blade to press said doctor blade against the roll, and a plurality of spaced adjusting members on said holder disposed to bear against the rear end of said pressure plate, said adjusting members being individually adjustable to cause pivotal movement of adjacent parts of the pressure plate about said nose and thereby to effect variations in the pressure applied by the pressure plate to the doctor blade at different points along its length and consequent variation in the doctoring pressure applied to the roll.

5. A doctor blade as claimed in claim 4 wherein said adjusting members bear directly against the rear end of said pressure plate.

6. A doctor as claimed in claim 5 wherein said adjusting members are screws.

7. A doctor as claimed in claim 4, which includes a deformable longitudinal bar disposed within the blade holder and interposed between the adjusting members and the rear end of the pressure plate. 

1. Structure for doctoring a roll of a papermaking machine comprising: an elongated, generally planar doctor blade having a longitudinally extending face and a longitudinal doctoring edge disposed generally in line contact with said roll; an elongated, generally planar pressure plate having a longitudinally extending face and a longitudinal pressure edge disposed generally in line contact with the face of the blade; a holder for the blade and the plate, said holder having an elongated abutment nose presenting a longitudinally extending fulcrum edge disposed generally in line contact with the face of the plate, said plate having a rear edge spaced from the pressure edge, said fulcrum edge contacting the plate at a location intermediate the rear edge and pressure edge thereof; and a series of individually adjustable, longitudinally spaced members carried by the holder, said members being disposed to bear against said plate at a location adjacent its rear edge for urging the plate about said fulcrum edge to vary the pressure between said pressure edge and the blade whereby to vary the doctoring pressure applied between the doctoring edge and the roll.
 2. Structure as set forth in claim 1 wherein said members comprise screws threadably engaged in said holder.
 3. Structure as set forth in claim 2 wherein a deformable bar is disposed between the screws and said plate.
 4. A doctor for a roll of a papermaking machine comprising a blade holder, a doctor blade accommodated in said holder for pivotal movement about its rear end with respect to the holder and adapted to bear at its front end against said roll, a pressure plate accommodated in the holder for pivotal movement about a nose on the holder which bears against the pressure plate at a location intermediate its front and rear ends, said pressure plate bearing at its front end against the doctor blade to press said doctor blade against the roll, and a plurality of spaced adjusting members on said holder disposed to bear against the rear end of said pressure plate, said adjusting members being individually adjustable to cause pivotal movement of adjacent parts of the pressure plate about said nose and thereby to effect vAriations in the pressure applied by the pressure plate to the doctor blade at different points along its length and consequent variation in the doctoring pressure applied to the roll.
 5. A doctor blade as claimed in claim 4 wherein said adjusting members bear directly against the rear end of said pressure plate.
 6. A doctor as claimed in claim 5 wherein said adjusting members are screws.
 7. A doctor as claimed in claim 4, which includes a deformable longitudinal bar disposed within the blade holder and interposed between the adjusting members and the rear end of the pressure plate. 